Switch the way we retrieve the vm_service_port from /hub to iquery, on device. (#114834)

packages/fuchsia_remote_debug_protocol/lib/src/fuchsia_remote_connection.dart

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 
 import 'package:process/process.dart';
@@ -506,32 +507,55 @@ class FuchsiaRemoteConnection {
     _pollDartVms = true;
   }
 
-  /// Gets the open Dart VM service ports on a remote Fuchsia device.
-  ///
-  /// The method attempts to get service ports through an SSH connection. Upon
-  /// successfully getting the VM service ports, returns them as a list of
-  /// integers. If an empty list is returned, then no Dart VM instances could be
-  /// found. An exception is thrown in the event of an actual error when
-  /// attempting to acquire the ports.
-  Future<List<int>> getDeviceServicePorts() async {
-    final List<String> portPaths = await _sshCommandRunner
-        .run('/bin/find /hub -name vmservice-port');
+  /// Helper for getDeviceServicePorts() to extract the vm_service_port from
+  /// json response.
+  List<int> getVmServicePortFromInspectSnapshot(dynamic inspectSnapshot) {
+    final List<Map<String, dynamic>> snapshot =
+        List<Map<String, dynamic>>.from(inspectSnapshot as List<dynamic>);
     final List<int> ports = <int>[];
-    for (final String path in portPaths) {
-      if (path == '') {
+
+    for (final Map<String, dynamic> item in snapshot) {
+      if (!item.containsKey('payload') || item['payload'] == null) {
+        continue;
+      }
+      final Map<String, dynamic> payload =
+          Map<String, dynamic>.from(item['payload'] as Map<String, dynamic>);
+
+      if (!payload.containsKey('root') || payload['root'] == null) {
         continue;
       }
-      final List<String> lsOutput =
-          await _sshCommandRunner.run('/bin/ls $path');
-      for (final String line in lsOutput) {
-        if (line == '') {
+      final Map<String, dynamic> root =
+          Map<String, dynamic>.from(payload['root'] as Map<String, dynamic>);
+
+      if (!root.containsKey('vm_service_port') ||
+          root['vm_service_port'] == null) {
         continue;
       }
-        final int? port = int.tryParse(line);
+
+      final int? port = int.tryParse(root['vm_service_port'] as String);
       if (port != null) {
         ports.add(port);
       }
     }
+    return ports;
+  }
+
+  /// Gets the open Dart VM service ports on a remote Fuchsia device.
+  ///
+  /// The method attempts to get service ports through an SSH connection. Upon
+  /// successfully getting the VM service ports, returns them as a list of
+  /// integers. If an empty list is returned, then no Dart VM instances could be
+  /// found. An exception is thrown in the event of an actual error when
+  /// attempting to acquire the ports.
+  Future<List<int>> getDeviceServicePorts() async {
+    final List<String> inspectResult = await _sshCommandRunner
+        .run("iquery --format json show '**:root:vm_service_port'");
+    final dynamic inspectOutputJson = jsonDecode(inspectResult.join('\n'));
+    final List<int> ports =
+        getVmServicePortFromInspectSnapshot(inspectOutputJson);
+
+    if (ports.length > 1) {
+      throw StateError('More than one Flutter observatory port found');
     }
     return ports;
   }